first-go-program

package main

import (
	"encoding/csv"
	"fmt"
	"io"
	"os"
	"sort"
)

var desiredColumns = []string{"id",
"date_registred",
"channel"
}

func indexOf(origin []string, column string) int {
	for i,  v := range origin {
		if column == v {
			return i
		}
	}
	return -1
}

func intersectMap(desired []string, columns []string) []int {
	idx := []int {}
	for _, v := range columns {
		if f := indexOf(desired, v); f > 0 {
			idx = append(idx, f)
		}
	}
	sort.Ints(idx)
	return idx
}

func cleanHeader(input []string) []string {
	ret := []string{}
	for _, v := range input {
		ret = append(ret, v[1:])
	}
	return ret
}

func main(){
	f, _ := os.Open("./1-customers.csv")
	r, _ := os.Create("./ret-1.csv")
	reader := csv.NewReader(f)
	columns, _ := reader.Read()
	line := cleanHeader(columns)
	desiredIdx := intersectMap(desiredColumns, line)
	csvWriter := csv.NewWriter(r)
	i := 0
	for {
		writeLine := []string{}
		for _, v := range desiredIdx {
			writeLine = append(writeLine, line[v])
		}
		if i== 0{
			fmt.Println(writeLine)	
		}
		i++
		csvWriter.Write(writeLine)
		var err error
		line, err = reader.Read()
		if err == io.EOF {
			break
		}
	}
}